A record $1 million reward has been offered for information to help find Sydney boy William Tyrrell, who disappeared from his grandmother's yard two years ago.
William, dressed in his favourite Spiderman suit, was last seen playing in the front yard of a house in Kendall on the NSW mid-north coast on the morning of September 12, 2014.
Police Commissioner Andrew Scipione said the case had "captured the hearts and minds of the nation".
Joined by Premier Mike Baird in Sydney on Monday Mr Scipione said the "unique reward" is "one million reasons why somebody that's out there that knows what's happened should come forward and talk to us".
"We've never had a $1 million reward ever before," he added.
Mr Baird hopes the substantial offer will help bring back William to his family.
"Two years ago today, the tragic disappearance of a young boy ... (was) an event that tore that family apart," he told reporters.
"Those million dollars, we hope, encourages anyone with any information to come forward to reunite William with his family."
The man in charge of the investigation, Chief Inspector Gary Jubelin, said it was "unacceptable that two years down the track we haven't found out what's happened to William".
He said police had numerous lines of inquiry and hoped the reward would be another tool.
Strike Force Rosann has taken information about nearly 700 persons of interest in relation to the case, and extra resources have been assigned to the investigation.
Police have previously said the then-three-year-old could have been the target of a pedophile ring operating in the north coast region.
"It is the state's largest investigation," Insp Jubelin said.
"We've had over 2,800 reports to Crime Stoppers alone from members of the public providing information. We have a further 196 reports directly to the strike force. We've had 1,078 sightings of William Tyrrell.
"We're identified 690 persons of interest," he said.
"I want to make it very clear that the fact that we've got so many persons of interest doesn't mean that we have no idea on what's happened," Inps Jubelin said.
Strikeforce Rosnan will also include assistance from the Armed Hold-up squad, the Sex Crimes squad, the Fraud squad as well as the Local Area Commands.
Insp Jubelin guaranteed protection for anyone who comes forward with information.
"I can guarantee personally that we can protect your identity. We can protect your safety," he said.
Washing machine repairman William "Bill" Spedding has been the most high-profile person to be questioned during the years-long investigation.
The 65-year-old has strenuously denied any involvement in William's disappearance and has not been arrested or charged in relation to the case.
The case has been referred to the NSW coroner but police say investigations continue with the hope the young boy is alive.